Polymer complexes. LXVI, thermal, spectroscopic studies and supramolecular structure of N-[β-(ethylamino)] acrylamide polymer complexes

Article abstract of DOI:10.1016/j.molliq.2016.03.086

Novel polymeric complexes with a potentially bidentate ligand N-[β-(ethylamino)] acrylamide (EA), formed by amidation of 1,2-diaminoethane with acryloyl chloride were synthesized and characterized on the basis of elemental analyses, IR,¹H NMR, UV-Vis, magnetic susceptibility measurements, ESR, molar conductance and thermal analysis. Molecular docking was used to predict the binding between EA ligand (keto and enol forms) and the receptor of prostate cancer mutant 2q7k-hormone and the receptor of breast cancer mutant 3hb5-oxidoreductase. The molecular and electronic structures of the different forms of the ligand are optimized theoretically and the quantum chemical parameters are calculated. The molar conductance data reveal that all the polymer complexes are non-electrolytes. Ligand (EA) has been shown to behave as neutral bidentate via its nitrogen atom of NH₂group and nitrogen atom of NH group in polymer complexes. On the basis of electronic spectral data and magnetic susceptibility measurements, suitable geometry has been proposed for each polymeric complex. The ESR spectral data of the Cu(II) complex showed that the metal-ligand bonds have considerable covalent character. The activation energies of the degradation of the polymer complexes were calculated.

Full text of DOI:10.1016/j.molliq.2016.03.086

Journal of Molecular Liquids 219 (2016) 1044–1057
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
Polymer complexes. LXVI, thermal, spectroscopic studies and
supramolecular structure of N-[β-(ethylamino)] acrylamide
polymer complexes
⁎
A.Z. El-Sonbati , M.A. Diab, A.A. El-Bindary, M.A. El-Mogazy
Chemistry Department, Faculty of Science, Damietta University, Damietta 34517, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
Novel polymeric complexes with a potentially bidentate ligand N-[β-(ethylamino)] acrylamide (EA), formed by
amidation of 1,2-diaminoethane with acryloyl chloride were synthesized and characterized on the basis of elemen-
tal analyses, IR, 1H NMR, UV–Vis, magnetic susceptibility measurements, ESR, molar conductance and thermal anal-
ysis. Molecular docking was used to predict the binding between EA ligand (keto and enol forms) and the receptor
of prostate cancer mutant 2q7k-hormone and the receptor of breast cancer mutant 3hb5-oxidoreductase. The mo-
lecular and electronic structures of the different forms of the ligand are optimized theoretically and the quantum
chemical parameters are calculated. The molar conductance data reveal that all the polymer complexes are non-
electrolytes. Ligand (EA) has been shown to behave as neutral bidentate via its nitrogen atom of NH2 group and ni-
trogen atom of NH group in polymer complexes. On the basis of electronic spectral data and magnetic susceptibility
measurements, suitable geometry has been proposed for each polymeric complex. The ESR spectral data of the
Cu(II) complex showed that the metal-ligand bonds have considerable covalent character. The activation energies
of the degradation of the polymer complexes were calculated.
Received 8 March 2016
Received in revised form 28 March 2016
Accepted 29 March 2016
Available online xxxx
Keywords:
Polymer complexes
ESR spectral
Spectroscopic and thermal studies
Molecular docking
Quantum chemical parameters
© 2016 Elsevier B.V. All rights reserved.
1. Introduction
Arshady et al. [5] were directed their attention towards polyamide
supports for which solvation compatibility with attached peptides
Acrylamide polymers have been important applications as floccu-
lants in the treatment of acid-leached uranium ores and oil-well stimu-
lation, and friction reduction but acrylamide polymers continue to enjoy
substantial markets as paper additives to increase dry strength and in
mineral processing [1]. Acrylamide polymers were considered impor-
tant class of water-soluble polymers. Acry1amide is a crystalline, rela-
tively stable monomer that is soluble in water and many organic
solvents. It readily undergoes polymerization by conventional free-
radical methods, but can also be polymerized photochemically, in the
solid state with ionizing radiation and anionically [2]. Chelating com-
pounds derived from acryloyl monomers are being utilized as suitable
ligands. They enable the formation of rigid coordination polymers.
Ghoneim et al. [3], were discussed preparation and structurally charac-
terization the acryloyl polymer complexes by different methods.
The relative stabilities of copper(II) and calcium(II) ions with the
polyampholytes containing ethylenediamine-N,N′-diacetic acid resi-
dues were discussed [4]. The free and two cross-linked polymers have
been studied by potentiometry and solution calorimetry. Copper(II) is
completely coordinated and the ligand acts as a sequestering agent.
could be readily envisaged. They were synthesized monomers (dimeth-
yl acrylamide, bis(acry1amido) ethane and N-(N-t-butoxycarbonyl-β-
alany1)-N′-acryloylhexamethylenediamine) provide directly a stable
cross-linked polymer appropriately functionalized for use in peptide
synthesis without further major modification [6].
In this paper, we will prepare polymer based on the reaction of 1,2-
diaminoethane (EDA) with acryloyl chloride (AC) to produce new acryl-
amide polymers, which having promising applications. Study ESR spec-
tral data of the Cu(II) complex and the thermal behavior of chelates the
polymer complexes. The molecular docking binding between EA ligand
(Fig. 1) and the receptors (2q7k-hormone and 3hb5-oxidoreductase)
are studied. Moreover, the molecular structures of the EA ligand are
studied and quantum chemical parameters are calculated.
2. Experimental
2.1. Materials
1,2-Diaminoethane (EDA) (BDH Chemical Ltd.) and acryloyl chloride
(AC) (Aldrich Chemical Co. Inc.) were used without further purification.
2,2′-Azobisisobutyronitrile (AIBN) (Aldrich Chemical Co. Inc.) was puri-
fied by dissolving in hot ethanol and filtering [7]. The solution was left to
cool. The pure material was collected by filtration and dried.
⁎
Corresponding author.
E-mail address: elsonbatisch@yahoo.com (A.Z. El-Sonbati).
http://dx.doi.org/10.1016/j.molliq.2016.03.086
0167-7322/© 2016 Elsevier B.V. All rights reserved.

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 219 (2016) 1044–1057
1045
Fig. 1. Synthesized monomer EA and PEA.
Fig. 2. 1H NMR spectrum of EA monomer.
2.2. Preparation of N-[β-(ethylamino)] acrylamide (EA) monomer
for 6 h. The polymer product was precipitated by pouring in distilled
water and dried in a vacuum oven for several days at 40 °C. The PEA ho-
mopolymer has been characterized by IR and 1H NMR spectra (Fig. 3).
N-[β-(ethylamino)] acrylamide (EA) monomer was prepared by the reac-
tion of equimolar amounts of acryloyl chloride (AC) (0.01 mol) 1,2-
diaminoethane (EDA) (0.01 mol) in dry benzene (25 mL) until the
evolution of hydrogen chloride ceased forming white powder of monomer.
The EA monomer has been characterized by IR and 1H NMR spectra (Fig. 2).
2.4. Preparation of the polymer complexes
Polymer complexes were prepared by refluxing anhydrous Cu(II),
Ni(II), Co(II), Cd(II) chlorides and UO2(NO3)2·5H2O (0.001 mol) with
the corresponding ligand (EA) (0.001 and/or 0.002 mol) in 20 mL
DMF as a solvent and 0.1% (w/v) AIBN as initiator. The resulting mixture
was heated at reflux for ~8 h. The hot solution was precipitated by
2.3. Preparation of poly N-[β-(ethylamino)] acrylamide (PEA) homopolymer
PEA homopolymer was prepared by free radical initiation of EA
(0.5 mol) using 0.1 w/v % AIBN as initiator and DMF (50 mL) as solvent
pouring in a large excess of distilled water containing dilute
Fig. 3. 1H NMR spectrum of PEA homopolymer.

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Table 1
Du Pont 950 thermobalance. Ten milligram samples were heated at a
rate of 10 °C/min in a dynamic nitrogen atmosphere (70 ml/min); the
sample holder was boat-shaped, 10 × 5 × 2.5 mm deep; the temperature
measuring thermocouple was placed within 1 mm of the holder. ESR
measurements of powdered samples were recorded at room tempera-
ture using an X-band spectrometer utilizing a 100 kHz magnetic field
modulation with diphenyl picrylhydrazyle (DPPH) as a reference materi-
al. This study simulates the actual docking process in which the ligand–
protein interaction energies are calculated using a Docking Server [10].
The MMFF94 Force field was used for energy minimization of ligand mol-
ecule using Docking Server. Gasteiger partial charges were added to the
ligand atoms. Non-polar hydrogen atoms were merged, and rotatable
bonds were defined. Docking calculations were carried out on EA ligand
protein models. Essential hydrogen atoms, Kollman united atom type
charges, and solvation parameters were added with the aid of AutoDock
tools [11]. Affinity (grid) maps of 0.375 Å spacing were generated using
the Autogrid program [12]. Auto Dock parameter set- and distance-
dependent dielectric functions were used in the calculation of the van
der Waals and the electrostatic terms, respectively. The molecular struc-
tures of the ligand were optimized by HF method with 3-21G basis set.
The molecules were built with the Perkin Elmer ChemBio Draw and opti-
mized using Perkin Elmer ChemBio3D software [13,14]. Quantum chem-
ical parameters such as the highest occupied molecular orbital energy
(EHOMO), the lowest unoccupied molecular orbital energy (ELUMO) and
HOMO–LUMO energy gap (ΔE) for the investigated molecules were
calculated.
Elemental analysesa of EA monomer and polymer complexes (for molecular structures,
see Figs. 1 and 13)b.
Compound
Exp. (calcd.) (%)
C
H
N
M
EA
52.44 (52.63) 8.63 (8.77) 24.21 (24.56)
–
EA-CuCl2 (1)
EA-CoCl2 (2)
EA-CdCl2 (3)
EA-NiCl2 (4)
24.00 (24.14) 3.89 (4.02) 10.88 (11.27) 25.35 (25.57)
24.45 (24.60) 3.98 (4.10) 11.16 (11.48) 23.87 (24.16)
19.79 (20.17) 3.21 (3.36) 9.23 (9.42)
37.66 (37.80)
33.34 (33.55) 5.34 (5.59) 15.45 (15.66) 16.23 (16.41)
EA-uranyl nitrate (5) 19.03 (19.29) 3.10 (3.22) 8.75 (9.00)
38.01 (38.27)
a
Microanalytical data as well as metal estimations are in good agreement with the stoi-
chiometry of the proposed complexes.
b
The excellent agreement between calculated and found data supports the assignment
suggest in the present work.
hydrochloric acid, to remove the metal salts that incorporated into the
polymer complexes. The polymer complexes were filtered, washed
with water, and dried in a vacuum oven at 40 °C for several days. The
polymer complexes were determined after decomposition by aqua-
regia, by complexometric titration using EDTA [8].
2.5. Measurements
Elemental microanalyses of the separated solid chelates for C, H and N
were performed in the Microanalytical Center. 1H NMR spectrum was ob-
tained with a Joel FX90 Fourier transform spectrometer with DMSO-d6 as
a solvent. Infrared spectra were recorded using Perkin-Elmer 1340 spec-
trophotometer and the spectra were recorded as KBr discs. Ultraviolet-
Visible (UV–vis) spectra of the polymer were recorded in Nujol mull
using a Unicom SP 8800 spectrophotometer. The magnetic moment of
the prepared solid complexes was determined at room temperature
using the Gouy's method. Mercury(II) (tetrathiocyanato)cobalt(II),
[Hg{Co(SCN)4}], was used for the calibration of the Gouy tubes. Diamag-
netic corrections were calculated from the values given by Selwood [9]
and Pascal's constants. Magnetic moments were calculated using the
3. Results and discussion
3.1. General
The 1:1 amidation of 1,2-diaminoethane and acryloyl chloride under
certain condition yielded the N-[β-(ethylamino)] acrylamide (EA)
monomer. Elemental analyses of the synthesized compounds are sum-
marized in Table 1. The analytical data agree well with the proposed for-
mula of the compounds. The synthetic mechanism of the principal
ligand is shown in Fig. 1. The ligand can exist either in the keto forms I
equation, μeff. = 2.84 [TχMcoor. 1/2
. TG measurements were made using a
]
Fig. 4. Tautomerism of EA monomer and PEA homopolymer .

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 219 (2016) 1044–1057
1047
Table 2
Energy values obtained in docking calculations of ligand (EA) with of prostate cancer mutant 2q7k and breast cancer mutant 3hb5 receptors.
Receptor Ligand
Est. free energy of binding
(kcal/mol)
Est. inhibition constant
(Ki) (μM)
vdW+ bond + desolve energy
(kcal/mol)
Electrostatic energy
(kcal/mol)
Total intercooled energy Interact
(kcal/mol)
surface
2q7k
3hb5
Keto form
−3.96
−3.98
−4.26
−3.39
1.25
1.21
759.29
3.27
−4.59
−4.28
−4.94
−4.85
−0.51
−0.53
−0.46
−0.03
−5.10
−4.81
−5.40
−4.88
304.346
300.208
297.089
376.244
Enol form
Keto form
Enol form
and III or enol forms II and IV (Fig. 4). However, the IR and 1H NMR
spectra of the ligand (EA) indicate that in the solid state it exists in
keto form. The molecular structure of the ligand is depicted in Fig. 4.
The physical analyses results indicate that the complexes synthesized
under the common solvent reaction have a 1:1/1:2 metal to ligand stoi-
chiometry, in which the ligand (EA) converts to the enol form and func-
tion as a neutral bidentate chelating agent coordinated to the metal ion,
while other coordination sites around the metal ion are completed by
the halogen molecules. Hence ligand and these polymer complexes
are prepared and completely characterized by various physico-
chemical techniques, viz. elemental analyses (C, H, N and metal con-
tent), IR, 1H NMR, solid reflectance, magnetic studies, ESR, molar con-
ductance and thermal analyses, as described below in detail. The
results of elemental analyses with molecular formula are presented in
Fig. 5. The ligand (keto and enol forms) (green in (A) and blue in (B)) in interaction with prostate cancer mutant 2q7k receptor. (For interpretation of the references to color in this figure
legend, the reader is referred to the web version of this article.)

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A.Z. El-Sonbati et al. / Journal of Molecular Liquids 219 (2016) 1044–1057
Table 1. The results obtained are in good agreement with those calculat-
ed for the suggested formula indicating the purity of the prepared
ligand.
3.3. Molecular structures
The optimized structures of the ligand (keto and enol forms) are
given in Fig. 11. The selected geometrical structures of ligand were cal-
culated. Selected geometric parameters bond lengths and bond angles
of ligand are tabulated in Tables 3 and 4.
3.2. Molecular docking
The docking study showed a favorable interaction between ligand
(keto and enol forms) and the prostate cancer (2q7k) and the breast
cancer (3hb5) receptors. The calculated energy is listed in Table 2 and
Figs. 5 and 6 for 2q7k and 3hb5 receptors, respectively. According to
the results obtained in this study, HB plot curve indicated that, the li-
gand binds to the two proteins hydrogen bond and decomposed inter-
actions energies in kcal/mol were existed between the ligand with
2q7k and 3hb5 receptors as shown in Figs. 7 and 8. The calculated effi-
ciency is favorable where Ki values estimated by AutoDock were com-
pared with experimental Ki values, when available, and the Gibbs free
energy is negative [15,16]. Also, based on this data, it can propose that
interaction between the 2q7k and 3hb5 receptors and the ligand is pos-
sible. 2D plot curves of docking with ligand are shown in Figs. 9 and 10.
It was found that the enol form of EA ligand shows best interaction with
2q7k receptor other than 3hb5 receptor.
The HOMO and LUMO of ligand (keto and enol forms) is shown
in Fig. 12. The enol form is more stable than the keto form as
reflected from energy gap values (Table 5). The HOMO–LUMO en-
ergy gap, ΔE, which is an important stability index, is applied to
develop theoretical models for explaining the structure and con-
formation barriers in many molecular systems [16]. The calculated
quantum chemical parameters are given in Table 5. Additional pa-
rameters such as ΔE, absolute electronegativities, χ, chemical po-
tentials, Pi, absolute hardness, η, absolute softness, σ, global
electrophilicity, ω, global softness, S, and additional electronic
charge, ΔNmax, have been calculated according to the following
equations [15,17]:
ΔE ¼ ELUMO−EHOMO
ð1Þ
Fig. 6. The ligand (keto and enol forms) (green in (A1) and blue in (B1)) in interaction with breast cancer mutant 3hb5 receptor. (For interpretation of the references to color in this figure
legend, the reader is referred to the web version of this article.)

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1049
Fig. 7. HB plot of interaction between ligand (a) keto form and (b) enol form with receptor of prostate cancer mutant 2q7k.

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A.Z. El-Sonbati et al. / Journal of Molecular Liquids 219 (2016) 1044–1057
Fig. 8. HB plot of interaction between ligand (a) keto form and (b) enol form with receptor of breast cancer mutant 3hb5.

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 219 (2016) 1044–1057
1051
Fig. 9. 2D plot of interaction between ligand (a) keto form and (b) enol form with receptor of prostate cancer mutant 2q7k.

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1
σ ¼
η
ð4Þ
Pi ¼ −χ
ð5Þ
ð6Þ
1
S ¼
2η
Pi2
ω ¼
ð7Þ
ð8Þ
2η
Pi
η
ΔNmax ¼ −
:
3.4. Elemental analyses of the polymer complexes
Reaction of the ligand with Cu(II), Co(II), Ni(II), Cd(II) and UO2(II)
ions, in the molar ratio 1:1/1:2 M:L), yielded polymer complexes a part
from the molar ratio. The prepared polymer complexes are stable at
room temperature, colored, non-hygroscopic and insoluble in water and
common organic solvents, but soluble in solvents such as DMF and DMSO.
The results of elemental analyses (Table 1) are in good agreement
with those required by the proposed formulae. The formation of these
polymer complexes proceeds according to the following equations:
AIBN
MCl2 ꢀ nH2O þ EA
½MðEAÞCl2ꢁn M ¼ CuðIIÞ ð1Þ; CoðIIÞ ð2Þor CdðIIÞ ð3Þ
Â
Ã
AIBN
NiCl2 ꢀ nH2O þ EA
NiðEAÞ2ðClÞ2 ð4Þ
n
Â
Ã
AIBN
UO2ðNO3Þ2 ꢀ 5H2O þ EA
UO2ðEAÞ2ðONO2Þ2 nð5Þ:
3.5. Molar conductance of the polymer complexes
The molar conductance of 10−3 M of solutions of the polymer com-
plexes in DMSO is calculated as 25 2 °C. It is concluded from the re-
sults that Cu(II), Co(II), Ni(II), Cd(II) and UO2(II) chelates with EA
ligand under investigation had molar conductance values in the range
from 2.35 to 12.60 Ω−1 mol−1 cm2 indicating their non-electrolytic na-
ture [18]. Hence the two chlorides in copper(II), cobalt(II), nickel(II) and
cadmium(II) polymer complexes are in the coordination sphere.
3.6. 1H NMR spectrum
The 1H NMR spectra of EA, PEA and its diamagnetic Cd(II) polymer
complex were recorded in d6-dimethylsulphoxide (DMSO-d6) solution
using tetramethylsilane (TMS) as internal standard. The 1H NMR spec-
trum of EA monomer (Fig. 2) showed the expected peaks and pattern
of the vinyl group (CH2 = CH) δ 6.25 ppm (dd, J = 17, 11 Hz) for the
vinyl CH proton and proton δ 5.12 ppm (AM part of AMX system dd,
J = 17, 1 Hz) for the vinyl CH2 protons, respectively. These peaks disap-
peared on polymerization while a triplet at δ 1.86 ppm (t, J = 7 Hz) and
a doublet at 1.80 ppm (d, J = 7 Hz) appeared, indicating that the poly-
merization of EA monomer occurs on the vinyl group [20]. The peaks at
2.9–3.1 ppm of EA monomer are due to the methylene groups of 1,2-
diaminoethane. The 1H NMR spectrum of PEA (Fig. 3) includes four res-
onances at 11.85, 5.55, 2.2 and 1.9 ppm relative to TMS which may be
assigned to the\\NH,\\NH2, vinylic\\CH\\and\\CH2 protons, respec-
tively [19]. There is a weak peak at 10.25 ppm due to the enolic\\OH
proton indicating that the ligand exist in enol form (Fig. 3), upon addi-
tion of D2O the intensities of both NH/OH, and NH2 protons significantly
decrease. The peaks at 10.30/11.75 ppm, which is due to the exchange-
able hydrogen-bonded hydroxyl/aminly (OH/NH) proton (Fig. 4). It dis-
appears upon exchange with D2O.
Fig. 10. 2D plot of interaction between ligand (a) keto form and (b) enol form with
receptor of breast cancer mutant 3hb5.
−ðEHOMO þ ELUMO
Þ
χ ¼
η ¼
ð2Þ
ð3Þ
2
ELUMO−EHOMO
2

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 219 (2016) 1044–1057
1053
Table 3
The selected geometric parameters for keto form ligand.
Bond lengths (Å)
Bond angles (o)
C(8)\\H(18)
C(8)\\H(17)
C(7)\\H(16)
N(6)\\H(15)
N(6)\\H(14)
C(5)\\H(13)
C(5)\\H(12)
C(4)\\H(11)
C(4)\\H(10)
N(2)\\H(9)
C(7)\\C(8)
C(1)\\C(7)
C(5)\\N(6)
C(4)\\C(5)
N(2)\\C(4)
C(1)\\O(3)
C(1)\\N(2)
1.1
H(15)\\N(6)\\H(14)
H(15)\\N(6)\\C(5)
H(14)\\N(6)\\C(5)
H(13)\\C(5)\\H(12)
H(13)\\C(5)\\N(6)
H(13)\\C(5)\\C(4)
H(12)\\C(5)\\N(6)
H(12)\\C(5)\\C(4)
N(6)\\C(5)\\C(4)
H(11)\\C(4)\\H(10)
H(11)\\C(4)\\C(5)
H(11)\\C(4)\\N(2)
H(10)\\C(4)\\C(5)
H(10)\\C(4)\\N(2)
C(5)\\C(4)\\N(2)
H(9)\\N(2)\\C(4)
H(9)\\N(2)\\C(1)
C(4)\\N(2)\\C(1)
H(18)\\C(8)\\H(17)
H(18)\\C(8)\\C(7)
H(17)\\C(8)\\C(7)
H(16)\\C(7)\\C(8)
H(16)\\C(7)\\C(1)
C(8)\\C(7)\\C(1)
C(7)\\C(1)\\O(3)
C(7)\\C(1)\\N(2)
O(3)\\C(1)\\N(2)
104.988
1.102
1.101
1.035
1.035
1.114
1.116
1.112
1.116
1.019
1.343
1.36
1.472
1.534
1.465
1.208
1.366
110.756
110.365
107.633
108.868
111.034
108.873
109.984
110.378
105.411
112.445
112.1
108.659
107.179
110.714
118.84
114.611
126.353
116.227
123.242
120.531
115.287
121.386
123.327
122.925
120.455
116.618
new band assigned to azomethine (C_N) and (OH) linkage appeared
at ≈1605 cm−1 and ≈3090 cm−1, respectively, in all polymer com-
plexes, indicating its participation in coordination [22]. This coordina-
tion is more likely than that of the other nitrogen because the basicity
is believed to decrease by inductive effect of the (C_N) group. The po-
sition of the band due to (OH) is unchanged, indicating non-
involvement of this group in complexation.
• New bands that appear in the polymer complexes at 425, 410, 440 and
445 cm−1 are attributed to υ(Cu-N), υ(Co-N), υ(Ni-N) and υ(Cd-N)
vibrations [23–25], respectively. The band at 280–340 cm−1 is
assigned to the υ(M-Cl) vibration.
Fig. 11. The calculated molecular structures of ligand (a) keto form and (b) enol form.
Table 4
3.7. IR spectra and mode of bonding
The selected geometric parameters for enol form ligand.
Bond lengths (Å)
Bond angles (o)
The IR spectra of the complexes are compared with those of the free
ligand in order to determine the coordination sites that may involve in
chelation. There are some guide peaks, in the spectrum of the ligand,
which are of good help for achieving this goal. These peaks are expected
to be involved in chelation such as NH2, CO and NH. The position and/or
the intensities of these peaks are expected to be changed upon chela-
tion. New peaks are also guide peaks in chelation. Upon comparison it
is found that:
The antisymmetric and symmetric (NH and NH2) stretching fre-
quencies appear in the region ~3425–3315 and 3480–3390 cm−1 in
the ligand, these frequencies have been considerable higher in the com-
plexes and this fact, along with changes in deformation, wagging and
rocking (NH2) vibrations suggest that the metals are coordinated via N
atom of the amino group. The participation of the NH2 group is further
confirmed by clarifying the effect of chelation on the in-plane bending,
δ(NH2) vibration. The shift of this band, from 1565 cm−1 in the free li-
gand to 1545–1585 cm−1 in the complexes indicates the participation
of the NH2 group in complexes formation [21].
C(8)\\H(18)
C(8)\\H(17)
C(7)\\H(16)
N(6)\\H(15)
N(6)\\H(14)
C(5)\\H(13)
C(5)\\H(12)
C(4)\\H(11)
C(4)\\H(10)
O(3)\\H(9)
C(7)\\C(8)
C(1)\\C(7)
C(5)\\N(6)
C(4)\\C(5)
N(2)\\C(4)
C(1)\\O(3)
C(1)\\N(2)
1.099
1.102
1.105
1.035
1.035
1.115
1.114
1.114
1.117
0.97
1.342
1.346
1.472
1.534
1.482
1.363
1.269
H(15)\\N(6)\\H(14)
H(15)\\N(6)\\C(5)
H(14)\\N(6)\\C(5)
H(13)\\C(5)\\H(12)
H(13)\\C(5)\\N(6)
H(13)\\C(5)\\C(4)
H(12)\\C(5)\\N(6)
H(12)\\C(5)\\C(4)
N(6)\\C(5)\\C(4)
H(18)\\C(8)\\H(17)
H(18)\\C(8)\\C(7)
H(17)\\C(8)\\C(7)
H(11)\\C(4)\\H(10)
H(11)\\C(4)\\C(5)
H(11)\\C(4)\\N(2)
H(10)\\C(4)\\C(5)
H(10)\\C(4)\\N(2)
C(5)\\C(4)\\N(2)
H(16)\\C(7)\\C(8)
H(16)\\C(7)\\C(1)
C(8)\\C(7)\\C(1)
H(9)\\O(3)\\C(1)
C(4)\\N(2)\\C(1)
C(7)\\C(1)\\O(3)
C(7)\\C(1)\\N(2)
O(3)\\C(1)\\N(2)
105.15
110.503
110.27
107.798
108.509
109.931
108.967
110.925
110.631
116.286
123.324
120.39
105.39
110.964
112.164
108.669
107.381
111.934
116.713
119.066
124.221
110.173
118.123
121.854
116.823
121.323
• The very sharp absorption band appeared in the free ligand at
≃1650 cm−1 is assigned to υ(C_O) group.
• IR spectrum of the ligand showed the absence of the bands due to car-
bonyl υ(C_O) and amino υ(NH) stretching vibration and instead a

1054
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 219 (2016) 1044–1057
Fig. 12. The Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) of ligand (a) keto form and (b) enol form.
• The dioxouranium (VI) polymer complex (5) exhibits υsym(O = U =
O) and υasym(O = U = O) at 794 and 919 cm−1, respectively, the
usual range for such complex [25,26] being υasym 870-950 and υasym
870-950 and υsym 780-955 cm−1. The force constant (FU-O) value is
6.8 × 10−8 N/Å which agree well with the force constant values of
similar dioxouranium(VI) complexes [26]. The U-O bond distance cal-
culated from the equation, RU-O = 1.17 + 1.08 f−1/3 is in the usual
range (1.60-1.92 Å) observed for dioxouranium(VI) complexes
[25-27]. In the polymer complex (5), the appearance of two new
bands in 1415 (υ5) and 1370 cm−1 (υ1) confirmed the monodentate
3.8. Magnetic susceptibility and electronic spectra measurements
Electronic spectrum of the ligand and their polymer complexes have
been measured in Nujol mull. All the polymer complexes show an intense
band in the 31,000–32,780 cm−1 range which is assigned to a π-π* tran-
sition associated with the azomethine linkage [28]. The spectra of the
polymer complexes show intense bands in the high-energy region in
the 20,800–28,160 cm−1 range which can be assigned to charge transfer
L → M bands [29]. The bands observed in the 20,620–27,900 cm−1 region
can be attributed to d-d transitions of the metal ions.
−
nature of the coordinated ONO2 group. The dioxouranium polymer
The electronic spectrum of Cu(II) polymer complex shows a broad
band at 14,295 cm−1. This is in agreement with those generally observed
for square planar Cu(II) complexes and can be due to 2B1g → 2A1g transi-
tion. The magnetic moment value of complex is 1.68 B.M., corresponding
to the spin value (1.73 B.M.), indicating the monomeric nature [30]. Elec-
tronic spectrum of EA-NiCl2 polymer complex shows three bands at 9900
complex exhibits a new band at ~ 24820-24680 cm−1, which is
u
assigned to the 1
∑
g
→
3πu transition, typical of OUO for the sym-
metric stretching frequency for the first excited state.
• The elemental analysis, IR, and the electronic spectra data indicate
that EA reacts with CuCl2, CoCl2, and CdCl2 in a 1:1 ratio; and with
NiCl2 and UO2(NO3)2 in 2:1 molar ratio (Fig. 13).
to 10,100, 16,500 and 23,810 to 24,400 cm−1 assigned to 3A2g
→
3T2g
In the present investigation, it is well established that uranyl ion pos-
sess planar hexagonal structure with nitrogen and oxygen atoms in
the axial position. Two ligands units and two NO−3 molecules remain
in the trans-position. The UO2(II) and Cd(II) polymer complexes are
found to be diamagnetic as expected. The geometry of Cd(II) complex
is square planar.
(F) (υ1) → 3T1g(F) (υ2) → 3T1g (P) (υ3) transitions, respectively. The li-
gand field parameters [B = 645, β = 0.62, Dq = 1010 cm−1 and υ2/
υ1 = 1.62 cm−1] in the same range reported for an octahedral structure
around Ni(II) [31]. The value of magnetic moment (3.15 B.M.) is an addi-
tional for an octahedral structure. However, the spectrum of Co(II) poly-
mer complex shows two bands (υ3) 4T2 → 4 T1(P) (14,715 cm−1) and
Table 5
The calculated quantum chemical parameters for ligand (keto and enol forms).
Compound
EHOMO (eV)
ELUMO (eV)
ΔE (eV)
χ (eV)
η (eV)
σ (eV)−1
Pi (eV)
S (eV)−1
ω (eV)
ΔNmax (eV)
Keto form
Enol form
−11.58
−11.13
−3.454
−3.043
8.128
8.087
7.518
7.087
4.064
4.044
0.246
0.247
−7.518
−7.087
0.123
0.124
6.954
6.209
1.849
1.753

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 219 (2016) 1044–1057
1055
Table 6
Weight loss percentage for PEA homopolymer and EA-metal chloride polymer
complexesa.
Polymer Volatilization First stage
Second stage Third stage
Tmax., Wt. Tmax., Wt.
Wt.%
remaining
at 1000 °C
temp., °C
Tmax., Wt.
°C
loss,% °C
loss,% °C loss,%
PEA
(1)
(2)
(3)
(4)
120
115
110
117
105
170
152
150
155
141
35
27
28
14
16
273
241
232
242
227
57
–
–
8
27
40
23
38
273
271
275
265
17
22
12
28
39
26
51
27
Fig. 13. The structures of M(II) complexes.
(υ2) 4A2 → 4 T1(F) (8300 cm−1) in the visible and near ir regions. The
values of 10Dq and B parameters calculated from the positions of υ3
and υ2 bands. These values are of the same order of magnitude as those
reported previously for the tetrahedral Co(II) complexes [32–34]. The
racah parameter value (B)(635 cm−1) of the free ion value (967 cm−1),
suggesting considerable orbital overlap [35]. The observed 10 Dq value
(4265 cm−1) shows that the N atoms of the ligand make effective contri-
bution to the ligand field in the complex. The magnetic moment value
(4.4 B.M.) indicative of tetrahedral geometry of the Co(II) complex.
a
Numbers as given in Table 1.
with g⊥ N gll N ge. For the present Cu(II) complex, the observed g-
values are gll (2.32) N g⊥ (2.09) N ge (2.0023), which suggest that
the unpaired electron lies in the dx2 − y2 [40] orbital. In the axial
spectra, the g-values are related with exchange interaction coupling
constant (G) by the following equation:
G ¼ gll−2=g⊥−2:
3.9. ESR spectrum
According to Hathaway and Billing [41], If G N 4, the exchange inter-
action between Cu(II) centers in the solid state is negligible. If G b 4, con-
siderable exchange interaction is indicated in the solid complex. The
observed value for the exchange interaction parameter for the copper
complex (G = 3.6) suggests that significant exchange coupling is
present and the misalignment is appreciable, and the unpaired electron
is present in the dx2 − y2 orbital. This result also indicates that the ex-
change coupling effects are not operative in the present complex. It is
usual to determine the bonding parameters for Cu(II) ion in various li-
gand field environments. The in-plane σ-bonding parameter, α2 is relat-
ed to gll and g⊥ by the following equation [40,42]:
The solid state ESR spectra of some complexes exhibit axially sym-
metric g-tensor parameters with ge b g⊥ N 2.0023 indicating that the
copper site has a dx2 − y2 ground state characteristic of tetrahedral,
square planer or octahedral stereochemistry [36]. Kivelson and Neiman
[37] have reported the gll value b2.3 for covalent character of the metal-
ligand bond and N2.3 for ionic character. Applying the criterion the co-
valent character of the metal-ligand bond in the complex under study
can be predicted. The trend gll N g⊥ N ge (2.0023) observed for this com-
plex shows that the unpaired electron is localized in dx2 − y2 orbital [38]
of the Cu(II) ion and the spectral features are characteristics of the axial
symmetry [39]. The complex under may have four coordinate square
geometry.
α2 ¼ All=0:036 þ ðgll−2:0023Þ þ 3=7ðg⊥−2:0023Þ þ 0:04:
In square planar complex, the unpaired electron lies in the dx2 − y2
orbital giving 2B1g as the ground state with gll N g⊥ N ge, while the un-
paired electron lies in the dz2 orbital giving 2A1g as the ground state
The α2 value of 0.72 indicates complete covalent bonding, while that
1.0 suggests complete ionic bonding. The observed value (0.72)
Fig. 14. TGA curves of PEA homopolymer and EA-metal chloride polymer complexes.

1056
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 219 (2016) 1044–1057
Table 7
indicates that the metal complexes are predominantly ionic in charac-
ter. The out-of-plane π-bonding (γ2) and in-plane π-bonding (β2) pa-
rameters are calculated using the following eqs.:
Activation energies of the thermal degradation of PEA
homopolymer and EA-matal chloride polymer
complexesa.
β2 ¼ ðgll−2:0023ÞE=−8λα2;
Polymer
Ea (kJ/mol)
PEA
(1)
(2)
(3)
(4)
13.7
12.2
11.7
12.9
11.2
γ2 ¼ ðg⊥−2:0023ÞE=−2λα2:
Here, λ = −828 cm−1 for free Cu(II) ion and E is the electronic en-
ergy for 2B1g
→
2A1g transition. The observed β2 value (0.95) and γ2
a
Numbers as given in Table 1.
value (1.05) indicate that there is interaction in the out-of-plane π-
bonding, whereas the in-plane π-bonding is predominantly ionic. This
is also confirmed by orbital reduction factors K, which can be estimated
from the simple relation [43]:
type of polymer complexes. The final weight residues, which can be
considered as metal oxide, are in good agreement with those calculated
from the metal content using EDTA. Table 6 shows the residual weight
percentage at 1000 °C.
The effective activation energies for the thermal degradation of PEA
and EA-metal salt polymer complexes were determined from the tem-
perature dependence of the chain rupture rate [44,45]. The rate constant
of the thermal degradation was plotted according Arrhenius relation-
ship (Fig. 15). Table 7 lists the activation energy of the thermal degrada-
tion (Ea) of PEA homopolymer and EA-metal salt polymer complexes.
The activation energy of the homopolymer is higher than that of the
polymer complexes. It is clear that the activation energies are in the
same order of the stabilities.
From the values of the activation energy of the thermal degradation
(Ea) of PEA homopolymer and complexes (1–4), it is observed that the
complexes (1–4) are less stable than the PEA homopolymer. These re-
sults are inconsistent with our previous results [13]. As shown in
Fig. 16, the activation energy (Ea) of the complexes is expected to in-
crease with the increasing thermal stability of complexes. Therefore,
the Ea value for the complex (1) is higher compared to the other com-
plexes (2 and 4), due to the higher atomic number which indicate that
the complex (1) is more stable than other complexes (2 and 4).
Kll ¼ α2β2;
K⊥ ¼ α2γ2:
Significant information about the nature of bonding in the Cu(II)
complex can be derived from the relative magnitude of Kll and K⊥. In
the case of pure σ-bonding, Kll ≈ K⊥ = 0.77, whereas Kll b K⊥ implies
considerable in-plane π-bonding, while for out-of-plane π-bonding
Kll N K⊥. For the present complex, the observed order K⊥(0.76) N Kll
(0.68) implies a greater contribution from in-plane π-bonding than for
out-of-plane π-bonding in metal-ligand π-bonding. Thus, the ESR
study of the copper complex has provided supporting evidence for the
optical results.
3.10. Thermal analyses
TG curves of PAH homopolymer and polymer complexes of EA with
CuCl2, CoCl2, NiCl2 and CdCl2 are shown in Fig. 14. PEA homopolymer
degrades in two stages. The first starts at ~120 °C with a weight loss of
35% and the second at ~190 °C with a weight loss of 57%. There are
three TG degradation stages for all the polymer complexes. The first
stage is due to the loss of chlorine molecules. Table 6 lists the percentage
of weight losses for each polymer complex and the maximum rate of
weight loss shown by the derivative equipment associated with the
TG apparatus. Their relative importance being dependent upon the
4. Conclusion
The ligand of N-[β-(ethylamino)] acrylamide (EA) behaves as a neu-
tral bidentate via its nitrogen atom of NH2 group and nitrogen atom of
NH group in polymer complexes. The polymer complexes characterized
on the basis of elemental analyses, IR, 1H NMR, UV–Vis spectra, magnet-
ic susceptibility measurements, ESR, molar conductance and thermal
analysis. Molecular docking and binding energy calculations of ligand
with prostate cancer mutant 2q7k-hormone and breast cancer mutant
3hb5-oxidoreductase receptors indicated that the ligand is efficient in-
hibitor of 3hb5-oxidoreductase and 2q7k-hormone receptors. It was
Fig. 15. Arrhenius plots for the degradation of PEA homopolymer and EA-metal chloride
polymer complexes.
Fig. 16. The relation between activation energy of the thermal degradation (Ea) and atomic
number of metal complexes (1, 2 and 4).

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 219 (2016) 1044–1057
1057
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